Just copy the 2020 tax return from the pc to the Mac using a flash drive. The Mac can read it. It is the file ending in .tax2020 and should be in your Documents in a Turbo Tax folder.
How to transfer into Mac Desktop
https://ttlc.intuit.com/community/tax-data-file/help/how-do-i-transfer-last-year-s-return-into-the-t...
